Cartridge systems constitute extremely practical constructions and methods for deploying almost any payload or projectile downrange. Typical cartridge systems incorporate the desired payload, a propellant, and some priming composition all within a self-contained unit. Ammunition cartridges are prototypical of cartridge devices, although cartridge systems have been used to launch chemical, pyrotechnic, marker, tracer, signaling, non-lethal, explosive, smoke, and other payloads to exploit their specific function.
Shotshell cartridges are complex ammunition cartridge systems that require additional components beyond the nominal propellant, projectile, and primer in order to effectively launch the desired projectiles. For example, a shotshell “wad” is the general term applied to the collection of components in a shotshell other than the projectile(s), the propellant, and the primer, which is used for effective delivery of the projectiles. Shotshell wads may be designed for various functions such as providing a seal against expanding propellant gases, containing and stabilizing the projectile(s) for a desired distance downrange, and/or cushioning and barrel protection.
While several configurations of shotshell components have been described for delivering a selected shot downrange, particular difficulties may arise when a single shotshell contains more than one size of projectile. These special purpose loads have found many applications in cartridges designed for hunting particular game and for self-defense. However, conventional loading methods such as adding buffer the shot can undesirably increase chamber pressure and complicate the loading process. Therefore, there exists a need for new cartridge designs that can effectively deliver two or more different sizes of projectiles downrange that are relatively simple and cost effective. Such designs would preferably use components that do not require additional costly tooling requirements for their manufacture, and desirably would seek to avoid the complicated features that can prohibitively increase costs.